In certain applications, the dimensional and structural integrity of certain critical components is of the utmost importance to assure against future service failures. An example of one such critical component is the cladding tube of a nuclear fuel rod, which contains the fuel pellet column. Plugs are welded to the open ends of the cladding tube to seal the pellet column therein. Cladding tubes must be manufactured to exacting standards of structural integrity if they are to withstand the high internal pressures developed over the long service life of nuclear fuel rods. That is, flaws, such as cracks, pores, etc., in the tube wall cross section, depending on their size, number and location, can render a cladding tube unsafe for use in a nuclear fuel rod.
Cladding tubes must also meet exacting dimensional standards. The inner diameter must be precisely controlled such that fuel pellets can be properly loaded therein. The same is true of the outer diameter so that the fuel rods can be properly assembled into fuel bundles. Wall thickness is also a rejection criteria, as a thin wall section less than a minimum tolerance dimension jeopardizes internal pressure withstandability.
In view of the critical nature of nuclear fuel rod cladding tubes, it is necessary to non-destructively inspect each and every cladding thoroughly over its entire length for both dimensional and structural integrity before it is accepted for use in a nuclear fuel rod. Ultrasonic inspection using a transducer operated in a pulse-echo mode is now being commonly utilized to examine critical components for quality assurance. The transducer is scanned over the component, by motion of the transducer and/or the component, while the transducer is periodically electrically excited to emit a probing ultrasonic energy pulse and, in the intervals between pulses, receives the echoes containing inspection information. The time required to fully inspect each component is largely dependent on scanning speed. Obviously, the scanning speed can not be so great that the transducer "runs away" from the probing energy pulse, such that it does not adequately receive the echoes associated with each pulse. To offset this limitation on scanning speed, multiple transducers have been utilized to reduce inspection time. This approach adds tremendously to the hardware cost of an ultrasonic inspection system, since each transducer calls for a separate signal channel, each with its own set of electronics for extracting inspection information from the echo signals.
It is accordingly an object of the present invention to provide an improved system for ultrasonically inspecting manufactured components.
A further object is to provide an ultrasonic inspection system of the above-character, which is capable of performing complete quality assurance inspection of manufactured components on an expedited, automated basis.
An additional object is to provide an ultrasonic inspection system of the above-character for quality assurance inspection of elongated, thin-walled tubular elements.
Another object is to provide an ultrasonic inspection system of the above-character for inspecting tubular elements for adherence to dimensional manufacturing standards and for the presence of structural flaws.
A still further object is to provide an ultrasonic inspection system of the above-character, which is economical in cost and efficient in operation.
Other objects of the invention will in part be obvious and in part appear hereinafter.